|  | 7.3 | Novell Routing
| 7.3.2 | Service advertising protocol
NetWare's SAP allows network resources, including file and print servers, to advertise their network addresses and the services they provide. Each service is identified by a number, called a SAP identifier. SAP updates are sent every 60 seconds. Intermediate network devices, like routers, listen to the SAP updates and build a table of all known services and associated network addresses. When a Novell client requests a particular network service, if a Netware server is located on the segment, it responds to the client request. The Cisco router does not respond to the GNS request. If there are no Netware servers on the local network, then the Cisco router responds with a server address from its own SAP table. The client can then contact the service directly. All the servers on NetWare networks can advertise their services and addresses. All versions of NetWare support SAP broadcasts to announce and locate registered network services. Adding, finding, and removing services on the network is dynamic because of SAP advertisements. Each SAP service is an object type identified by a number. The following are examples:
Number | SAP Service
4 | NetWare file server
7 | Print server
24 | Remote bridge server (router)
Workstations do not keep SAP tables-only routers and servers keep SAP tables. All servers and routers keep a complete list of the services available throughout the network in SAP tables. Like RIP, SAP also uses an aging mechanism to identify and remove SAP table entries that become invalid. By default, service advertisements occur at 60-second intervals. However, although service advertisements might work well on a LAN, broadcasting services can require too much bandwidth to be acceptable on large networks, or in networks linked on WAN serial connections. Routers do not forward SAP broadcasts. Instead, each router builds its own SAP table and forwards the SAP table to other routers. By default, this occurs every 60 seconds, but the router can use access control lists to control the SAPs accepted or forwarded. Cisco IOS software also allows network administrators to display SAP table entries by name rather than by SAP identifier. By presenting network configuration information in a more readable format, this feature makes maintaining networks and diagnosing network problems easier.
| Engineering Journal
Configurable RIP and SAP Update Timers and Packet Sizes